Lathe speed change mechanism

raffreyturner · 18 Jan 2013

HI,
I'm new to this - never owned a lathe before. I have a Charnwood 813 which is has problems with the speed change device. After rough turning a bowl at low speed, I found it difficult to raise the speed for finer turning. The belt drive appears to go very loose once you turn up the spindle speed. So even though the speed increases ( a bit), a very light touch of the bowl gouge is enough to bring it to a halt. Would appreciate any advice on what ought to happen to keep the belt under tension as the spindle pulley expands. It's a new belt by the way.
thanks

CHJ · 18 Jan 2013

Make sure that the Motor Pulley shaft is lubricated, (grease point in the end) and the outer spring loaded pulley half moves along the motor shaft.

You may have to resort to some thin penetrating oil to get it moving, just make sure you remove surplus so that it does not get on belt.

Take care with any levering of the pulleys, they are brittle and easily damaged.

raffreyturner · 18 Jan 2013

Thanks for your response Chas,

I thought the motor pulley wheel looked like it should be moving - and it clearly isn't just now. I have WD40'd it as a starting point and will leave it overnight to do its work (anyway there are several inches of snow twixt me and the garage just now!)

Thanks again - advice much appreciated.

raffreyturner · 20 Jan 2013

Update:

I had to dismantle the spring fitting to persuade the pulley to move on the shaft. A tap or two at the base of the pulley got it moving, and and a little cleaning with several applications of oil got everything sliding smoothly again. The circlip came off easily - and I managed to find it (which was a pleasant surprise). A visit to a friend produced a set of circlip pliers which made replacing it a simple process. Pleased to report my lathe is now running better than ever before.

thanks for the guidance

CHJ · 20 Jan 2013

Glad you you managed to sort it, these type of drives thrive on a regular clean-up and a bit of TLC. a lot depends of course on the usage of the machine but with my old machine which had a daily use with a similar drive I gave it a clean out and lube once a month, just a small squirt of grease on the motor shaft and some dry PTFE lube on the headstock mechanism.

A couple of other points, if you have speed problems in the other direction check that the inner motor pulley flange has not become loose and moved nearer the motor and if you start to detect any sloppiness in the speed lever mechanism check that any locking grub screws and location pins are as they should be in the headstock area.

Don't try to change speeds without at least turning the chuck by hand, the belt needs the pulleys to be rotating to move its position.